The standard 4.2-liter six-cylinder engine is smooth and powerful, and it's the perfect companion for the standard Envoy. The heavier XL and XUV models really need the optional 5.3-liter V8, though.The 4.2-liter inline-6 is a modern engine with dual overhead camshafts, four valves per cylinder, and variable phasing for the exhaust cam to produce 275 horsepower and 275 pound-feet of torque. That's more horsepower than the Ford Explorer's optional 4.6-liter sohc V8 and nearly as much torque. About 90 percent of the GMC's peak torque is available at just 1600 rpm, and it's still there at 5600 rpm.
That means quick response at any engine speed, allowing the Envoy to bound past trucks on steep uphill two-lanes with confidence. In the standard-wheelbase Envoy, the 4.2-liter six is rated 16/21 mpg city/highway with 2WD. It's an excellent engine, and with its broad and bountiful torque, the transmission does much less downshifting. Stand on the gas and the full-throttle upshift comes at about 6000 rpm, and the engine feels like it's only striding, not screaming. The smooth-shifting four-speed automatic transmission is the proven Hydramatic 4L60-E, used in GM applications from Corvettes to Cadillac Escalades. A 3.42:1 rear-end ratio is standard for maximum economy, but ratios of 3.73 and 4.10 are offered for easier towing. With so much torque available, we couldn't discern a significant improvement in acceleration performance with the 4.10. Towing was a high engineering priority, and the six-cylinder, standard-wheelbase Envoy is rated to pull 6100 pounds with 4WD, and 6300 pounds with 2WD.
The V8 is standard in Denali, and optional in XL and XUV. Refined for 2005, it now develops 300 horsepower and 330 pound-feet of torque, easily topping the Explorer V8. Equipped with the V8, an Envoy XL can tow 7100 pounds with 2WD, or 6700 pounds with 4WD. All Envoys come with a trailer hitch platform and seven-wire trailer harness.
For 2005, long-wheelbase Envoys with the V8 are now equipped with Displacement on Demand (DOD) technology, which shuts down four of the eight cylinders when they are not needed, for up to 8 percent better fuel mileage under light-load conditions. The engine-management computer instantly revives the sleeping cylinders the second the driver demands more go. With this system, even the 5000-pound 4WD XUV can squeeze 15/18 city/highway miles out of a two-dollar gallon.
The standard Envoy feels smooth and stable at high speeds. It rides smooth and car-like at lower speeds without being overly soft in corners. On a high-speed washboard surface, the rear end stayed impressively planted. The Envoy is designed to lean exactly 5 degrees in corners, and then stop leaning. Envoy's track is among the widest in the class. Also, the engine is mounted relatively low, lowering the Envoy's center of gravity. A low center of gravity means better handling and stability. On the downside, the Envoy has a relatively low ground clearance of 8 inches under the engine, reducing its capability for serious off-highway driving.
The optional load-leveling air suspension is intended to provide a more luxurious ride. It uses a silent air compressor, which yields one additional benefit: a 22-foot air hose that attaches to a small valve in a compartment in the cargo area, and can be used for filling everything from tires to toys. Off-road, we found that the load-leveling suspension bottomed easily, signaling a need for the optional skid plates. Our test model had the skid plates, of course, which we dragged in soft sand, chugging easily along at 5 mph in Auto4WD. On low-speed whoop-de-doos, the front end bobbed up and down more than we would have liked.
The Envoy's four-wheel-drive system, called Autotrac, works well and features four settings: 2WD, Auto4WD, 4HI and 4LO. Auto4WD shifts power to all four wheels as conditions require. Switching in and out of 4WD can be done on the fly with a flip of the switch (although the transmission must be in neutral to engage or disengage 4LO).We tested the Auto4WD mode by deliberately driving into soft sand in 2WD. The moment the Envoy bogged, we switched to Auto4WD on the fly; it clicked in and began pulling us right along again. (Of course, it makes more sense to stay in 4WD if you think you might encounter soft sand.) Auto4WD is especially good in mixed, inconsistent conditions, such as ice or patchy snow. For serious off-road use, it's usually best to switch to 4HI or, for low-speed mud-slogging or climbing steep, rugged terrain, 4LO.
The four-wheel anti-lock disc brakes are impressive. The Envoy's nose doesn't dive under hard braking, keeping the vehicle remarkably level and stable.
The longer Envoy XL and XUV lack the responsiveness and handling of the standard-length Envoy. The Envoy XL is long and narrow and feels it. Envoy XL's wheelbase is stretched dramatically, by 16 inches. And its suspension is soft. It wallows in corners. On exit ramps, when braking and turning at the same time, the Envoy XL does not inspire confidence an Envoy or a Yukon does. On the highway, the XL wanders around in its lane. Stability is also affected by strong crosswinds at high speeds. The XL needs all the power it can get from the V8, given that it weighs nearly 350 pounds more than the standard Envoy. The XUV drives very similarly to the XL.
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